eina/debug: rework session thread destruction to avoid deadlock on shutdown

when debugging was active, this would frequently result in the monitor thread
blocking in a read() call for a fd which had already been closed by the main
thread. the main thread would be waiting for the monitor thread to fail its read()
and destroy itself, but the read() would never end without an interrupt

this reworks the monitor thread destruction to stop relying on the thread to
remove its session from the session list and instead only access the list from
the main thread, allowing sessions to always be immediately destroyed

fix T7103

1 files changed, 16 insertions, 15 deletions

diff --git a/src/lib/eina/eina_debug.c b/src/lib/eina/eina_debug.c
index 6420496786..dbce08d04a 100644
--- a/src/lib/eina/eina_debug.c
+++ b/src/lib/eina/eina_debug.c
@@ -132,6 +132,8 @@ struct _Eina_Debug_Session
    void *data; /* User data */
    int cbs_length; /* cbs table size */
    int fd; /* File descriptor */
+   Eina_Lock lock; /* deletion lock */
+   Eina_Bool deleted : 1; /* set if session is dead */
 };
 
 #ifndef _WIN32
@@ -271,6 +273,17 @@ eina_debug_session_terminate(Eina_Debug_Session *session)
    /* Close fd here so the thread terminates its own session by itself */
    if (!session) return;
    close(session->fd);
+   eina_lock_take(&session->lock);
+   if (session->deleted)
+     {
+        eina_lock_release(&session->lock);
+        free(session);
+     }
+   else
+     {
+        session->deleted = 1;
+        eina_lock_release(&session->lock);
+     }
 }
 
 EAPI void
@@ -451,6 +464,7 @@ _session_create(int fd)
    if (!session) return NULL;
    session->dispatch_cb = eina_debug_dispatch;
    session->fd = fd;
+   eina_lock_new(&session->lock);
    eina_spinlock_take(&_thread_delete_lock);
    sessions = eina_list_append(sessions, session);
    eina_spinlock_release(&_thread_delete_lock);
@@ -586,12 +600,8 @@ _monitor(void *_data)
           }
         else
           {
-             close(session->fd);
              _opcodes_unregister_all(session);
-             eina_spinlock_take(&_thread_delete_lock);
-             sessions = eina_list_remove(sessions, session);
-             free(session);
-             eina_spinlock_release(&_thread_delete_lock);
+             eina_debug_session_terminate(session);
              break;
           }
      }
@@ -736,22 +746,13 @@ Eina_Bool
 eina_debug_shutdown(void)
 {
    Eina_Debug_Session *session;
-   Eina_List *l;
    pthread_t self = pthread_self();
 
    eina_spinlock_take(&_thread_delete_lock);
-   EINA_LIST_FOREACH(sessions, l, session)
+   EINA_LIST_FREE(sessions, session)
      eina_debug_session_terminate(session);
    eina_spinlock_release(&_thread_delete_lock);
 
-   while (1)
-     {
-        eina_spinlock_take(&_thread_delete_lock);
-        if (!sessions) break;
-        eina_spinlock_release(&_thread_delete_lock);
-     }
-   eina_spinlock_release(&_thread_delete_lock);
-
    _eina_debug_timer_shutdown();
    _eina_debug_bt_shutdown();
    _eina_debug_cpu_shutdown();